Defining representativeness of study samples in medical and population health research.

Medical and population health science researchers frequently make ambiguous statements about whether they believe their study sample or results are representative of some (implicit or explicit) target population. This article provides a comprehensive definition of representativeness, with the goal of capturing the different ways in which a study can be representative of a target population. It is proposed that a study is representative if the estimate obtained in the study sample is generalisable to the target population (owing to representative sampling, estimation of stratum specific effects, or quantitative methods to generalise or transport estimates) or the interpretation of the results is generalisable to the target population (based on fundamental scientific premises and substantive background knowledge). This definition is explored in the context of four covid-19 studies, ranging from laboratory science to descriptive epidemiology. All statements regarding representativeness should make clear the way in which the study results generalise, the target population the results are being generalised to, and the assumptions that must hold for that generalisation to be scientifically or statistically justifiable.

Prospective Cohort Study of Cryptosporidium Infection and Shedding in Infants and Their Households.

BACKGROUND: Cryptosporidium spp. are responsible for significant diarrheal morbidity and mortality in under-5 children. There is no vaccine; thus, a focus on prevention is paramount. Prior studies suggest that person-to-person spread may be an important pathway for transmission to young children. Here we describe a longitudinal cohort study of 100 families with infants to determine rates of cryptosporidiosis within households during the coronavirus disease 2019 (COVID-19) pandemic. METHODS: Families living in Mirpur, Bangladesh, with 1 infant aged 6-8 months were enrolled and followed with weekly illness survey and stool testing for Cryptosporidium for 8 months. RESULTS: From December 2020 to August 2021, 100 families were enrolled. Forty-four percent of index children and 35% of siblings had at least 1 Cryptosporidium infection. Shedding of Cryptosporidium occurred for a mean (standard deviation) of 19 (8.3) days in index infants, 16.1 (11.6) days in children 1-5 years, and 16.2 (12.8) days in adults. A longer duration of Cryptosporidium shedding was associated with growth faltering in infants. There was a spike in Cryptosporidium cases in May 2021, which coincided with a spike in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cases in the region. CONCLUSIONS: In this intensive, longitudinal study of Cryptosporidium infection in families we found high rates of cryptosporidiosis in infants and children, and prolonged parasite shedding, especially among malnourished children. These data support that transmission within the household is an important route of exposure for young infants and that treatment of nondiarrheal infection to interrupt person-to-person transmission within the home may be essential for preventing cryptosporidiosis in infants.

Post-sequelae symptoms and comorbidities after COVID-19.

The frequency, severity, and forms of symptoms months after coronavirus 2019 (COVID-19) are poorly understood, especially in community settings. To better understand and characterize symptoms months after community-based COVID-19, a retrospective cohort analysis was conducted. Three hundred and twenty-eight consecutive persons with a positive test for SARS-CoV-2 in the Johns Hopkins Health System, Maryland, March-May 2020, were selected for the study. Symptom occurrence and severity were measured through questionnaires. Of 328 persons evaluated, a median of 242 days (109-478 days) from the initial positive SARS-CoV-2 test, 33.2% reported not being fully recovered and 4.9% reported symptoms that constrained daily activities. Compared to those who reported being fully recovered, those with post-acute sequelae were more likely to report a prior history of heart attack (p < 0.01). Among those reporting long-term symptoms, men and women were equally represented (men = 34.8%, women = 34.6%), but only women reported symptoms that constrained daily activities, and 56% of them were caregivers. The types of new or persistent symptoms varied, and for many, included a deviation from prior COVID-19 health, such as being less able to exercise, walk, concentrate, or breathe. A limitation is that self-report of symptoms might be biased and/or caused by factors other than COVID-19. Overall, even in a community setting, symptoms may persist months after COVID-19 reducing daily activities including caring for dependents.

Genomics in the era of COVID-19: ethical implications for clinical practice and public health.

Genomic studies of patients with COVID-19, or exposed to it, are underway to delineate host factors associated with variability in susceptibility, infectivity, and disease severity. Here, we highlight the ethical implications-both potential benefits and harms-of genomics for clinical practice and public health in the era of COVID-19.

The Role of Host Genetic Factors in Coronavirus Susceptibility: Review of Animal and Systematic Review of Human Literature.

The SARS-CoV-2 pandemic raises many scientific and clinical questions. These include how host genetic factors affect disease susceptibility and pathogenesis. New work is emerging related to SARS-CoV-2; previous work has been conducted on other coronaviruses that affect different species. We reviewed the literature on host genetic factors related to coronaviruses, systematically focusing on human studies. We identified 1,832 articles of potential relevance. Seventy-five involved human host genetic factors, 36 of which involved analysis of specific genes or loci; aside from one meta-analysis, all were candidate-driven studies, typically investigating small numbers of research subjects and loci. Three additional case reports were described. Multiple significant loci were identified, including 16 related to susceptibility (seven of which identified protective alleles) and 16 related to outcomes (three of which identified protective alleles). The types of cases and controls used varied considerably; four studies used traditional replication/validation cohorts. Among other studies, 30 involved both human and non-human host genetic factors related to coronavirus, 178 involved study of non-human (animal) host genetic factors related to coronavirus, and 984 involved study of non-genetic host factors related to coronavirus, including involving immunopathogenesis. Previous human studies have been limited by issues that may be less impactful now, including low numbers of eligible participants and limited availability of advanced genomic methods; however, these may raise additional considerations. We outline key genes and loci from animal and human host genetic studies that may bear investigation in the study of COVID-19. We also discuss how previous studies may direct current lines of inquiry.